Effects of green tea on weight loss and weight maintenance. A meta-analysis

Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM) Maastricht University, Maastricht, The Netherlands.
International journal of obesity (2005) (Impact Factor: 5). 07/2009; 33(9):956-61. DOI: 10.1038/ijo.2009.135
Source: PubMed


Different outcomes of the effect of green tea on weight loss (WL) and weight maintenance (WM) have been reported in studies with subjects differing in ethnicity and habitual caffeine intake.
To elucidate by meta-analysis whether green tea indeed has a function in body weight regulation.
English-language studies about WL and WM after green tea supplementation were identified through PubMed and based on the references from retrieved articles. Out of the 49 studies initially identified, a total of 11 articles fitted the inclusion criteria and provided useful information for the meta-analysis. Effect sizes (mean weight change in treatment versus control group) were computed and aggregated based on a random-effects model. The influence of several moderators on the effect sizes was examined.
Catechins significantly decreased body weight and significantly maintained body weight after a period of WL (microcirc=-1.31 kg; P<0.001). Inhibition of this effect by high habitual caffeine intake (>300 mg per day) failed to reach significance (microcirc=-0.27 kg for high and microcirc=-1.60 kg for low habitual caffeine intake; P=0.09). Also, the seemingly smaller effect of catechins in Caucasian (microcirc=-0.82 kg) subjects compared with Asians (microcirc=-1.51 kg; P=0.37) did not reach significance. Interaction of ethnicity and caffeine intake was a significant moderator (P=0.04).
Catechins or an epigallocatechin gallate (EGCG)-caffeine mixture have a small positive effect on WL and WM. The results suggest that habitual caffeine intake and ethnicity may be moderators, as they may influence the effect of catechins.

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Available from: Rick Hursel, Sep 09, 2015
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    • "While the present study was conducted to examine the effect of IQP-GC-101 on Caucasian subjects, it is suggested that the interaction of two factors, habitual caffeine intake and ethnicity, may impact the effect of green tea catechins-caffeine on body weight regulation. A systematic review of green tea in weight loss showed that Caucasians having a higher coffee intake tended to tolerate the effect of caffeine and thus showed a lower weight loss in response to treatment with EGCG and coffee, compared with Asians with low coffee intake (Hursel et al., 2009). Likewise , while all subjects were committed to adhere to a slightly hypocaloric diet with 30% of energy coming from fat, strict control of daily dietary calories intake was not implemented, and impact of deviations from daily recommended dietary calories intake was not quantified. "
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    ABSTRACT: IQP-GC-101 is a patented blend of the standardized extracts of Garcinia cambogia, Camellia sinensis, unroasted Coffea arabica, and Lagerstroemia speciosa. These individual ingredients of IQP-GC-101 have each shown promise in promoting weight loss; however, the efficacy of the blend has not been established. This randomized, placebo-controlled, double-blind, parallel group study conducted over 14 weeks (including a 2-week run-in phase) aimed to investigate the efficacy and safety of IQP-GC-101 in reducing body weight and body fat mass in overweight Caucasian adults. Subjects took three IQP-GC-101 or placebo tablets, twice a day, 30 min before main meals. All subjects also adhered to a 500 kcal/day energy deficit diet with 30% of energy from fat. Ninety-one overweight and mildly obese subjects (46 in the IQP-GC-101 group, 45 in the placebo group) completed the study. After 12-week intervention, IQP-GC-101 resulted in a mean (±SD) weight loss of 2.26 ± 2.37 kg compared with 0.56 ± 2.34 kg for placebo (pU = 0.002). There was also significantly more reduction in body fat mass, waist circumference, and hip circumference in the IQP-GC-101 group. No serious adverse events were reported. The use of IQP-GC-101 has been shown to result in body weight and body fat reduction in the current study, with good tolerability. © 2014 InQpharm Group Sdn Bhd. Phytotherapy Research published by John Wiley & Sons, Ltd.
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    • "The toll-like receptor 4 (TLR4) pathway mediates the inflammatory process induced by diet rich in saturated fats, leading to proinflammatory cytokines synthesis and secretion [8], and inhibition of downstream signals of the TLR4 pathway — such as inhibitor of κB kinase β/nuclear factor κB (IKKβ/NF-κB) — in the hypothalamus prevented dietinduced obesity, as well as insulin and leptin resistance [9]. Prevention of obesity costs much less than its treatment and daily consumption of green tea (Camellia sinensis) is an interesting approach, as it induces weight loss or weight maintenance in adult subjects [10]. We demonstrated that green tea extract (GTE) reduced mass of adipose tissue depots and attenuated the mesenteric adipose tissue inflammatory response to high-fat diet (HFD) [11]. "
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    ABSTRACT: To investigate possible mechanisms of green tea’s anti-obesity and anti-diabetic effects in the hypothalamus, the central regulator of metabolism, of mice fed with high-fat diet, we analysed proteins of the toll-like receptor 4 pathway and serotoninergic proteins involved in energy homeostasis. Thirty days old male Swiss mice were fed with high-fat diet rich in saturated fat and green tea extract for eight weeks. After that, body weight and mass of fat depots were evaluated. Oral glucose tolerance test was performed three days prior to euthanasia; serum glucose, insulin and adiponectin were measured in fasted mice. Hypothalamic toll-like receptor 4 pathway proteins, serotonin receptors 1B and 2C, and serotonin transporter were analysed by Western blotting or enzyme-linked immunosorbent assay. A second set of animals was used to measure food intake in response to fluoxetine, a selective serotonin reuptake inhibitor. Mice fed with high-fat diet had increased body weight and mass of fat depots, impaired oral glucose tolerance, elevated glucose and insulin, and decreased adiponectin serum levels. Toll-like receptor 4, IκB-α, nuclear factor κB p50, and interleukin-6 were increased by high-fat diet. Concomitant green tea extract treatment ameliorated these parameters. The serotoninergic system remained functional after high-fat diet treatment, despite a few alterations in protein content of serotonin receptors 1B and 2C, and serotonin transporter. In summary, the green tea extract attenuated the deleterious effects of the high-fat diet investigated in this study, partially due to reduced hypothalamic inflammation.
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    • "However, a thermogenic effect as well as a weight reducing effect has not been unanimously shown, indicating the presence of moderating factors. The difference in outcome between several ethnic populations suggests a role for genetic predisposition, which was supported by recent meta-analyses [10], [11] that addressed effects of GT on weight loss and thermogenesis. Different polymorphisms for COMT enzyme activity exist and these may be responsible for the variability in flavonoid O-methylation that was previously reported by Hodgson et al. [12]. "
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